Fuel pump wiring route

[angus337]

I'm in the process of tidying up the wiring in the passenger footwell. Plan is to remove all the redundant wiring and install a new relay panel.

I'm a bit confused though with the fuel pump relay wiring, which is different to the standard 14cux wiring diagram.

The 14cux wiring diagram shows a single purple/white outlet to the pump, via the interia switch. However, on mine there are two outputs, a thin purple/white wire which seems to be routed to the engine bay, and a thicker black wire.

The black wire runs though the loom to the black plug with the 3 looped wires, then back to a brown plug behind the dash. The outlet from the brown plug is yellow and black, which I think runs directly to the inertia switch. This sort of makes sense. But no idea what the thin purple/white wire does. Any ideas?

[Belle427]

I believe it goes to the charcoal canister solenoid valve.

[Steve_D]

Belle427 said:

I believe it goes to the charcoal canister solenoid valve.

Correct.

Steve

[angus337]

Cheers, will leave it connected for now.

Theres also the grey/orange wire from pin 17 on the ECU which is listed as Purge control valve outlet. I didnt expect megasquirt to have this output, but it is connected internally on my ECU. So think I'll leave this one in too, until I can figure out if it does anything.

For the fuel pump supply, I guess it would be ok to connect directly from the relay output to the inertia switch, and bypass the route via the black and brown plugs?


It a bit of a mess at the moment! But making progress.

Edited by angus337 on Sunday 17th May 22:46

[Belle427]

I chose to rewire my fuel pump as I didn’t like how many joints are in the loom to it and didn’t want any further problems with my Megasquirt conversion.
I went from the inertia switch up over the transmission tunnel and drilled a new hole near the pump for the cables, I earthed it directly to battery too.
I didn’t trace the circuit out but im pretty sure it goes off to the immobiliser from the brown plug you mention that’s usually behind the radio, so just be aware of this if you start bypassing loom sections.
I’m not really sure either what purpose that section of black loop back connections are there for.

Edited by Belle427 on Monday 18th May 07:02

[Belle427]

To save confusion on my car it went from fuel pump relay output, through those loop back connectors and then to the brown plug.

[angus337]

So I've pretty much got the wiring all sorted and ready to test.

The one thing that's still bugging me though, is the loom with the black wires and loop back plug, which ideally I'd like to cut out.

I've traced the wires from the three loops across across the plug which make sense, so it should be possible to bypass these. However I can't figure out what the 4 thinner wires do as they just seem to terminate at the plug socket. Can these be safely cut and terminated or are they connected internally within in the plug.

[Belle427]

I don’t think they are linked internally, I believe these are the immobiliser circuits and this is a method to confuse thieves but I’m not 100% sure on that last bit.
This is useful.
http://www.bertram-hill.com/fuel-pump-schematic.ht...

[Steve_D]

Those black wires at the connector are the immobiliser circuit so you need to be very careful before you go cutting them or you could end up with a very dead car.

As an aside this is not the 'Loopback' connector that you may have seen people refer to.

Steve

[angus337]

Theres 9 wires in total connected to the black plug.

I'm pretty sure of the wiring route for the 3 main circuits that have the loops on the plug.

Fuel pump -- FP relay > pin 2 > pin 3 > immobiliser via brown plug
Starter --- immobiliser > pin 6 > pin 10 > starter solenoid (this is the loop that is cut when fitting the hot start mod)
Ingntion -- switched live from brown plug> blue plug in loom > pin 8 > pin 4 > ignition amp (not required)

I've just checked the other pins:

Pin 1 > ground from engine bay (not used?)
Pin 5 > also switched live spliced to same input as pin 8 (not used)
Pin 9 > to engine bay ( not used?)

So my plan is as follows:

Disconnect at pin 3 and connect directly to the FP relay
Disconnect at pin 10 and connect to hot start relay output
Disconnect at pin 6 and connect to hot start relay trigger.

I dont think this will affect the immobiliser operation. The rest I'll safely cut and terminate once I've tested it.

[Belle427]

Sounds like you have it in hand but just be careful as if there are grounds in it you may have issues.
Not sure if it’s been confirmed or not but this thread suggests there may be lambda grounds there?
https://www.pistonheads.com/gassing/topic.asp?h=0&...

[angus337]

Tested today with the stripped down loom, had a few issues getting the fule pump to prime, which turned out to be the inertia switch which needed resetting.

Removed this lot:



And still have all these unused wires to trace and terminate.



And then wrap the loom, and secure the battery and ECU.

[Belle427]

Getting somewhere now, there are quite a few spare wires for the air con if you don’t have it fitted.

[Penelope Stopit]

Lovely job

Have no fear, rip it out is what it's all about

Nice, very nice

Can't remember if you intend to move the fusebox?

[Steve_D]

angus337 said:

..............And still have all these unused wires to trace and terminate..............

PM me the wire colours and I will see if I can identify them for you.
Can also supply circuit diagram that may help.

Steve

[angus337]

Thanks for the offer steve, but I think I've managed to remove all the wires. Here's the main loom to the ecu.






At the moment the plan is to leave the fuse box where it is. Although I have fitted new fuses for the injectors, coil pack, starter, fuel pump and wideband next to the relay block under the dash. Trial fitted for now, as still need to tidy up and secure the wiring.

[Penelope Stopit]

Hate those crush-on connectors but do appreciate the effort made

Think of the weight loss

[angus337]

I've tried to avoid crimp connectors, the only ones crimped at the moment are to are to the wideband, all the others are soldered on with heat shink over the top. I'm also tring to find a better quality fuse box to replace the cheap Halfords offering.

[ez64]

Having problems with my fuel pump priming after leaving the car to sit for two weeks. Traced the problem logically, relays working as they should and 12v showing at the relay output on prime or forced on via RoverGauge. However underneath the car at the wiring terminals for the fuel pump I have 6-7v so there must be resistance somewhere.


I'll trace the wiring via this thread but I'm tempted to remove my immobiliser anyway as I don't want it, just wanted to check if others have had a similar problem perhaps with the inertia switch causing the high resistance on the FP circut?

[Belle427]

ez64 said:

Having problems with my fuel pump priming after leaving the car to sit for two weeks. Traced the problem logically, relays working as they should and 12v showing at the relay output on prime or forced on via RoverGauge. However underneath the car at the wiring terminals for the fuel pump I have 6-7v so there must be resistance somewhere.


I'll trace the wiring via this thread but I'm tempted to remove my immobiliser anyway as I don't want it, just wanted to check if others have had a similar problem perhaps with the inertia switch causing the high resistance on the FP circut?

Earlier in this thread is a link to a schematic which shows some connectors in the b pillar area behind the carpet.
Check here first, if it were my car I’d bypass it correctly here with solder and shrink to save future issues.